We've been tracking the trends from ComScore, Hitwise, Nielsen/NetRatings, and NetApplications since the beginning of 2007, and the numbers don't paint a pretty picture for anyone other than Google. In particular, both of Microsoft's major search properties—Live Search and MSN—have experienced mostly negative growth over the past year and a half, mostly to the benefit of Google. While Yahoo has scuffled for share fractions with MSN and Live over a couple quarters in 2007, MSN has seen the worst (and steady) decline in market share from a peak of 9.15 percent in February 2007 to just 5.46 percent, according to Hitwise data. Considering a heavy cross-promotion with NBC's Olympic site—MSN powers the search and provides portions of live coverage on its home page—things could improve after August's numbers are out. But still, a loss of that much market share hurts.

Data source: Comscore

As you can see, Nielsen/NetRatings sees things a bit differently than the other three firms. According to their metrics, Microsoft has seen solid growth since the beginning of 2007. In January of that year, Microsoft managed to grab 8.9 percent of the search market. For June 2008, the latest month for which Nielsen/NetRatings has released date, Microsoft search properties have grabbed 14.1 percent of the market. The big loser in this scenario is Yahoo, which dropped from 22.7 percent to 16.6 percent during the same time period. Unfortunately for both Microsoft and Yahoo, Google has grown from 53.7 percent to 59.0 percent during those 18 months by NNR's reckoning.

Data source: Nielsen/NetRatings

NetApplications is another source of bad news for Microsoft, which breaks the numbers out by Microsoft property. Live Search has fared better than its portal sibling over the past year and a half, as to be expected with Microsoft throwing so much weight behind it as a stand-alone Google competitor and heavily marketing Live brand of web applications as a whole. Unfortunately, the lost MSN search market share hasn't translated into increased share for Windows Live. Microsoft began offering incentives to businesses in March 2007 for getting employees to make a Live Search switch, then extended its pay-to-search (or perhaps more accurately: shop) model to the general consumer in May this year. A series of major overhauls have increased Live Search's index, UI, and results, and Microsoft even introduced a program for the automotive industry to easily incorporate Live Search services into cars. The takeway from NetApplications is that Microsoft's Live strategy has yet to show much in the way of results when it comes to search share.

Data source: Hitwise

Yahoo is a mixed bag. Comscore essentially has Yahoo's search traffic heading into the toilet, if not swirling down the bowl. Although Yahoo has seen a modest bump to 20.9 percent since bottoming out at 20.4 percent share in April, it's a far cry from the 28.1 percent market share the portal enjoyed at the onset of 2007. The other metrics firms also have Yahoo on a downward trend, but not as severe a drop as Comscore shows.

Data source: NetApplications

One thing that all four firms agree on: Google rules. NetApplications has the search giant over 78 percent worldwide as of July, while Comscore has its search share growing from 47.5 percent to 61.5 percent from January 2007 to June 2008. Nielsen/NetRatings paints a slightly different, but still positive picture for Google. As mentioned above, Google has gained 5.3 percentage points of search share over the past 18 months, but the company has been on a downward slope since its April high of 62 percent.

The bottom line is that, at least so far, a lot of the rumbling from Yahoo and Microsoft of open search enhancements and paidsearch incentives hasn't made a dent in Google's expanding search empire. Whether users are simply rooted in their Googling ways or Sergey and Larry's special sauce really is that special, it's readily apparent why Microsoft really wanted Yahoo's search business.